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Volumn 44, Issue 17, 1991, Pages 9764-9767

Measurements of the temperature dependence of the magnetic penetration depth in YBa2Cu3O7- superconducting thin films

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EID: 0000038383     PISSN: 01631829     EISSN: None     Source Type: Journal    
DOI: 10.1103/PhysRevB.44.9764     Document Type: Article
Times cited : (121)

References (45)
  • 12
    • 84927822856 scopus 로고    scopus 로고
    • B. W. Langley, S. M. Anlage, and M. R. Beasley (unpublished); B. W. Langley, Ph.D. thesis, Stanford University, 1991.
  • 15
    • 84927822855 scopus 로고    scopus 로고
    • The slopes of the lines in Figs. 1 and 2, as well as their shape, are somewhat sensitive to the choice of vp(0) / c, which comes from extrapolation of the data to T=0. We are more confident about the slopes derived from the Y-Ba-Cu-O data because extends down to T / Tc= 0.1.
  • 16
    • 84927822854 scopus 로고    scopus 로고
    • The Nb and NbCN films were sputtered by J. Murduck at TRW, Redondo Beach, from Nb targets in Ar and Ar-N-2 CH4 atmospheres, respectively. The Nb film has Tc= 9.2 K and residual resistivity ratio (RRR) of 4 with ρ ( 0 ) = 4 μ Ω cm and thickness 3650 Å. The NbCN film has a Tc= 15.8 K, RRR of 1.1, ρ ( 0 ) = 60 μ Ω cm, and thickness 5660 Å.
  • 20
    • 34250425065 scopus 로고
    • The BCS λ ( T ) is calculated using an isotropic scaled weak-coupling theory by the method of
    • (1974) Z. Phys. , vol.266 , pp. 209
    • Halbritter, J.1
  • 21
    • 84927822853 scopus 로고    scopus 로고
    • By varying 2 Δ ( 0 ) / kBTc with this method one can examine the effects of strong coupling without resorting to more elaborate theories. Parameters for Nb are Tc= 9.0 K, lMFP= 130 Å, λL= 390 Å, and ξ0= ( 2 / π ) ξF= 380 Å, and for NbCN Tc= 18.0 K, lMFP= 100 Å, λL= 2300 Å, and ξ0= 50 Å.
  • 22
    • 84927822852 scopus 로고    scopus 로고
    • S. I. Park, Ph.D. thesis, Stanford University, 1986;
  • 24
    • 84927822851 scopus 로고    scopus 로고
    • D. M. Sheen et al. (unpublished); D. E. Oates et al. (unpublished).
  • 27
    • 84927822850 scopus 로고    scopus 로고
    • Parameters chosen for YBaCu32 O7-δ are ξF= ( π / 2 ) ξ0= 15 Å, λL= 1400 Å, lMFP= 100 Å, and Tc= 90 K (see Ref. 18).
  • 41
    • 84927822848 scopus 로고    scopus 로고
    • The fit values of λseries( 0 ) is close to the value of 1400 Å taken for the domains, but is quite different from the value calculated from the equation for λseries( T ). This is because fits to the data do not make use of the magnitude of the fitting function, only its temperature dependence.
  • 42
    • 84927822847 scopus 로고    scopus 로고
    • In general we find a strong dependence of λ ( 0 ) on the temperature dependence used to fit the data (see Refs. 6–8, 11) as others have (see Ref. 5). This problem is common to all measurement techniques that do not uniquely determine a zero-temperature baseline.
  • 43
    • 84927822846 scopus 로고    scopus 로고
    • If the weak links are taken to be grain boundaries [with a = 1 mum (Ref. 16) and Jc( 0 ) = 2 times 106 A/cm2] instead of the twin boundaries, the fit parameters are almost identical: 2 Δ ( 0 ) / kBTc= 4.5, Δstar( 0 ) = 8 meV. Hence the weak links can originate from several different kinds of defects.


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